Years ago, general wisdom held that transit systems must bring people into a city's central business district. The idea was to create a corridor from home to job. But the idea and the systems remained long after jobs left the city center.

The mindset is changing in some cities — in one recent example, reported by our Emily Badger a few months back, Tallahassee decentralized its entire bus system. And generally speaking, these multi-destination transit systems have been much more effective than the downtown-only systems they replaced. They're generally more productive than their counterparts, according to recent research, carrying more passengers at lower cost:

But while multi-destination transit systems may be better suited to modern life than their radial predecessors, it's unclear whether or not they divert passengers from single-occupancy vehicles. That's because transit riders can be broadly divided into two categories: "dependent" riders, people who are more or less forced to ride given the high cost of car ownership, and "choice" riders, those who simply prefer riding to driving.

A new study from the Mineta Transportation Institute tries to compare and contrast these two transit populations, using the city of Atlanta as an example. The study leaders use data from the 2000 Census, as well as a detailed examination of Atlanta's multi-destination bus and rail systems, to identify variables most important to each group.

Their overriding purpose, they report, is to pinpoint policies that might increase the share of choice riders taking transit, while preserving the core of the multi-destination systems that offer so much benefit to dependent riders.

The first thing the researchers noticed, in line with previous research, is that dependent transit riders tend to take the bus and choice riders tend to take rail. Bus/dependent riders tend to come from lower-income zones and has less access to a car, compared with rail/choice riders. Unlike their bus-riding counterparts, rail riders place a premium on out-of-vehicle travel time — in other words, they don't like when it takes a long time to get to a transit station. The central business district is a major destination for rail riders, and they also seem to prefer going through transit-oriented developments. Neither of these factors plays a major role in bus/dependent travel, according to the report; on the contrary, bus riders are trying to reach lower-density employment centers.

At the same time, the two types of riders have much in common. Both are sensitive to in-vehicle travel time, as well as the time it takes to transfer. A quarter of all rail riders transfer to bus to complete their trip, according to the study, which suggests that intermodal transfers are critical as well. And even though rail riders head to the downtown core more often than bus riders, areas with a large number of jobs — though not necessarily high-density employment centers — remain a key destination for both groups.

The way to attract both choice and dependent riders, then, is to create a transit network that traverses the center district and still extends deep into low-density employment corridors; that improves access to transit-oriented developments, as well as the developments themselves; and that expedites the transfer process — particularly intermodal transfers.

In short, the authors suggest that Atlanta and other cities keep the core principles of the multi-destination system and make them bigger, stronger, faster:

These results derive from a study of Atlanta, Georgia, but given their consistency with lessons derived from other locales, they provide important policy guidance to transit agencies seeking to increase ridership by both rider groups. Certainly, more money would be needed first to develop such a system and then to operate it, but the characteristics of transit demand from Atlanta reported here and the performance of multi-destination transit systems elsewhere suggest that an expanded multi-destination transit network in Atlanta would have beneficial results. Regional riding habits would increase substantially without sacrificing productivity, while operating cost per passenger would decline. Both transit-dependent and choice riders would use this expanded network in larger numbers than they use the present one.

Of course, as the authors hint at only briefly in this concluding statement, the proposal here is easier outlined than implemented. The study has done a service to the literature by illuminating, or at the very least reinforcing, a basic understanding of dependent and choice rider preferences. But it stops short of the pressing concern faced by transit agencies across the countries these days: where to get the money to achieve real change.

Without that practical push, either from other scholars or actual policymakers, the discussion remains an abstraction — the type of mental exercise that might at least kill some time while you await your transfer.

About the Author

Eric Jaffe is a senior associate editor at CityLab. He writes about transportation as well as behavior, crime, and history, and has a general interest in the science of city life. He's the author of A Curious Madness (2014) and The King's Best Highway (2010), and lives in New York.